The present invention generally relates to data communication apparatuses, and more particularly to a data communication apparatus which is connected to two telephone lines.
Recently, facsimile machines are becoming popular and there are facsimile machines which have a built-in telephone circuit so that one facsimile machine has both the functions of a telephone and a facsimile machine. In the present application, an apparatus which has the functions of the telephone and the facsimile machine is referred to as a data communication apparatus. FIG. 1 shows an example of a conventional data communication apparatus.
In FIG. 1, a data communication apparatus 1 generally comprises a switch 2, an off-hook switch 3, a ringer circuit 4, a conversation circuit 5, a handset 6, a dialer circuit 7, a ten-key 8, a controller 9, a ringing (call) detection circuit 10, a modem 11, a unit part 12, and a line protection unit 13. The off-hook switch 3, the ringer circuit 4, the conversation circuit 5 and the dialer circuit 7 constitute a telephone circuit 14.
In an initial state of the data communication apparatus 1, the switch 2 connects a telephone line L to the telephone circuit 14 and the ringing detection circuit 10, and the telephone line L is coupled to the ringer circuit 4 through the off-hook switch 3. When a ringing (call) is received through the telephone line L, the ringer circuit 4 rings a ringing element while the ringing detection circuit 10 detects the ringing and supplies a ringing (call) detection signal to the controller 9. When the ringer circuit 4 rings, an operator unhooks the handset 6 and the off-hook switch 3 connects the telephone line L to the conversation circuit 5 to enable a conversation through the handset 6. In a case where a caller is a facsimile machine, the operator pushes a start key (not shown) of the data communication apparatus 1 so that the switch 2 couples the telephone line L to the modem 11 through the line protection circuit 13 and enables a facsimile communication. When the caller simply wishes to make a conversation, the operator can make the conversation through the handset 6 by not pushing the start key.
The data communication apparatus 1 has an automatic reception mode for automatically receiving a facsimile transmission. When the ringer circuit 4 rings but the handset 6 is not unhooked for a predetermined time in a state where the data communication apparatus 1 is set to the automatic reception mode, the controller 9 supplies a switching signal to the switch 2 so as to couple the telephone line L to the modem 11 and automatically receive a facsimile communication.
When making a facsimile transmission or a telephone call, the operator unhooks the handset 6 and enters a telephone number of a destination from the ten-key 8. In this case, the dialer circuit 7 sends a dial signal to the telephone line L through the off-hook switch 3. Thereafter, the conversation can be made through the handset 6. When making the facsimile transmission, a transmission key of the data communication apparatus 1 for making a facsimile transmission is pushed prior to entering the destination telephone number from the ten-key 8. When the transmission key is pushed, the controller 9 supplies a switching signal to the switch 2 after the destination telephone number is entered so as to couple the telephone line L to the modem 11 and enable the facsimile transmission.
For the sake of convenience, the unit part 12 shown in FIG. 1 generally refers to parts of the data communication apparatus 1 other than the parts shown.
However, the conventional data communication apparatus 1 is connected to a single telephone line L and one telephone circuit 14 is required with respect to this single telephone line L. For this reason, when the data communication apparatus 1 needs to be connected to two telephone lines L, it is necessary to provide two telephone circuits 14 within the data communication apparatus 1.
FIG. 2 shows an essential part of a conventional data communication apparatus 20 which is connected to two telephone lines L1 and L2. The data communication apparatus 20 comprises a telephone circuit 21 with respect to the telephone line L1 and a telephone circuit 22 with respect to the telephone line L2. Switches 23 and 24 are controlled to connect the telephone circuit 21 to the telephone line L1 or the telephone circuit 22 to the telephone line L2 to make a telephone call. On the other hand, the switches 23, 24 and 25 are controlled to connect the modem 26 to either one of the telephone lines L1 and L2 to make a facsimile communication. However, there is a problem in that the data communication apparatus 20 becomes bulky and expensive because of the need to provide the two telephone circuits 21 and 22.